1. Field of the Invention
The present invention relates to movable body drive methods and movable body drive systems, pattern formation methods and apparatuses, exposure methods and apparatuses, device manufacturing methods, and measuring methods, and more particularly to a movable body drive method and a movable body drive system in which a movable body is driven along a substantially two-dimensional plane, a pattern formation method using the movable body drive method and a pattern formation apparatus equipped with the movable body drive system, an exposure method using the movable body drive method and an exposure apparatus equipped with the movable body drive system, a device manufacturing method using the pattern formation method, and a measuring method to measure unevenness of the movable body surface.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing electron devices (microdevices) such as semiconductor devices (such as integrated circuits) and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner) are mainly used.
However, the surface of a wafer serving as a substrate subject to exposure is not always flat, for example, by undulation and the like of the wafer. Therefore, especially in a scanning exposure apparatus such as a scanner and the like, when a reticle pattern is transferred onto a shot area on a wafer by a scanning exposure method, positional information (focus information) related to an optical axis direction of a projection optical system of the wafer surface as detected at a plurality of detection points set in an exposure area, for example, using a multiple point focal point position detection system (hereinafter also referred to as a “Multipoint AF system”) and the like, and based on the detection results, a so-called focus leveling control is performed (refer to, for example, U.S. Pat. No. 5,448,332) to control the position in the optical axis direction and the inclination of a table or a stage holding a wafer so that the wafer surface constantly coincides with an image plane of the projection optical system in the exposure area (the wafer surface is within the focal depth of the image plane).
Further, with the stepper or the scanner and the like, wavelength of exposure light used with finer integrated circuits is becoming shorter year by year, and numerical aperture of the projection optical system is also gradually increasing (higher NA), which improves the resolution. Meanwhile, due to shorter wavelength of the exposure light and larger NA in the projection optical system, the depth of focus had become extremely small, which caused a risk of focus margin shortage during the exposure operation. Therefore, as a method of substantially shortening the exposure wavelength while substantially increasing (widening) the depth of focus when compared with the depth of focus in the air, the exposure apparatus that uses the immersion method has recently begun to gather attention (refer to, for example, the pamphlet of International Publication No. 2004/053955).
However, in the exposure apparatus using this liquid immersion method or other exposure apparatus whose distance (working distance) between the lower end surface of the projection optical system and the wafer is small, it is difficult to place the multipoint AF system in the vicinity of the projection optical system. Meanwhile, in the exposure apparatus, in order to realize exposure with high precision, realizing surface position control of the wafer with high precision is required.
Further, with the stepper or the scanner or the like, position measurement of the stage (the table) which holds a substrate (for example, a wafer) subject to exposure was performed in general, using a laser interferometer having a high resolution. However, because the optical path length of the laser interferometry beam which measures the position of the stage is around several hundred mm or more, and also because position control of the stage with higher precision is becoming required due to finer patterns owing to higher integration of semiconductor devices, short-term variation of measurement values which is caused by air fluctuation which occurs due to the influence of temperature fluctuation or temperature gradient of the atmosphere on the beam path of the laser interferometer can no longer be ignored.
Accordingly, instead of the interferometer, it is conceivable that a sensor system which directly measures positional information (surface position information) of the surface of the table in the optical axis direction is used, however, in such a system, there are various kinds of causes of error which are different from the interferometer.